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use std::hash::Hash;
use rustc_hash::FxHashMap;
/// There are two principle ways to refer to things:
/// - by their locatinon (module in foo/bar/baz.rs at line 42)
/// - by their numeric id (module `ModuleId(42)`)
///
/// The first one is more powerful (you can actually find the thing in question
/// by id), but the second one is so much more compact.
///
/// `Loc2IdMap` allows us to have a cake an eat it as well: by maintaining a
/// bidirectional mapping between positional and numeric ids, we can use compact
/// representation wich still allows us to get the actual item
#[derive(Debug)]
pub(crate) struct Loc2IdMap<L, ID>
where
ID: NumericId,
L: Clone + Eq + Hash,
{
loc2id: FxHashMap<L, ID>,
id2loc: FxHashMap<ID, L>,
}
impl<L, ID> Default for Loc2IdMap<L, ID>
where
ID: NumericId,
L: Clone + Eq + Hash,
{
fn default() -> Self {
Loc2IdMap {
loc2id: FxHashMap::default(),
id2loc: FxHashMap::default(),
}
}
}
impl<L, ID> Loc2IdMap<L, ID>
where
ID: NumericId,
L: Clone + Eq + Hash,
{
pub fn loc2id(&mut self, loc: &L) -> ID {
match self.loc2id.get(loc) {
Some(id) => return id.clone(),
None => (),
}
let id = self.loc2id.len();
assert!(id < u32::max_value() as usize);
let id = ID::from_u32(id as u32);
self.loc2id.insert(loc.clone(), id.clone());
self.id2loc.insert(id.clone(), loc.clone());
id
}
pub fn id2loc(&self, id: &ID) -> L {
self.id2loc[id].clone()
}
}
pub(crate) trait NumericId: Clone + Eq + Hash {
fn from_u32(id: u32) -> Self;
fn to_u32(self) -> u32;
}
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